This invention relates to microorganisms and their use to degrade N-phosphonomethylglycine in an aqueous solution, such as a waste stream, by biodegradation.
N-Phosphonomethylglycine, known in the agricultural chemical art as glyphosate, is a highly effective and commercially important phytotoxicant, useful in controlling the growth of germinating seeds, emerging seedlings, maturing and established woody and herbaceous vegetation, and aquatic plants. N-phosphonomethylglycine and its salts are conveniently applied in an aqueous formulation as a post-emergent phytotoxicant for the control of numerous plant species. N-phosphonomethylglycine and its salts are characterized by a broad spectrum activity, i.e., the control of a wide variety of plants.
Numerous methods are known in the art for the preparation of N-phosphonomethylglycine. For example, U.S. Pat. No. 3,969,398 to Hershman discloses a process for the production of N-phosphonomethylglycine by the oxidation of N-phosphonomethyliminodiacetic acid utilizing a molecular oxygen-containing gas as the oxidant in the presence of a catalyst consisting essentially of activated carbon. U.S. Pat. No. 3,954,848 to Franz disclose the oxidation of N-phosphonomethyliminodiacetic acid with hydrogen peroxide and an acid such as sulfuric acid. U.S. Pat. No. 4,670,190 to Kleiner discloses a process for the preparation of N-phosphonomethylglycine by reacting aminomethylphosphonic acid and glyoxylic acid in a molar ratio of about 1 to 2 in an aqueous medium or aqueous organic medium at temperatures between 30.degree. and 100.degree. C. These references are only illustrative since there are many other methods known in the art for preparing N-phosphonomethylglycine.
Regardless of the process by which N-phosphonomethylglycine is prepared, all of these processes produce aqueous, waste streams that contain small amounts of N-phosphonomethylglycine and various by-products and unreacted starting materials, such as N-phosphonomethyliminodiacetic acid, N-formyl-N-phosphonomethylglycine, aminomethylphosphonic acid, formaldehyde, and the like. Such waste streams should be kept to a minimum to help preserve the environment. (M. L. Rueppel, et al., "Metabolism and Degradation of Glyphosate in Soil and Water", Journal of Agriculture and Food Chemistry, Vol. 25 (1977) p. 517-522).
It is known that certain natural microorganisms will degrade N-phosphonomethylglycine over a period of time. In addition, several microorganisms have been isolated which will degrade N-phosphonomethylglycine. For example, G. S. Jacob, et al., "Metabolism of Glyphosate in Pseudomonas sp. Strain LBr", Applied and Environmental Microbioloy, Vol. 54, No. 12 (Dec. 1988) p 2953-2958, reports the metabolism of glyphosate by Pseudomonas sp. Strain LBr. L. E. Hallas, et al., "Characterization of Microbial Traits Associated with Glyphosate Biodegradation in Industrial Activated Sludge", Journal of Industrial Microbiology, 3 (1988) p 377-385 reports that the microorganisms from two industrial activated sludges that treat N-phosphonomethylglycine waste streams were enumerated by microscopic examination. It was suggested that the degradation activity is not a universal trait, and its expression requires enrichment through specific selective pressures. T. M. Balthazor, et al., "Glyphosate-Degrading Microorganisms from Industrial Activated Sludge", Applied and Environmental Microbiology, Vol. 51 No. 2 (Feb. 1986) p 432-434, discloses a plating medium to isolate microorganisms that will degrade N-phosphonomethylglycine as the sole phosphorus source. One purified isolate metabolized N-phosphonomethylglycine to aminomethylphosphonic acid was identified as a Flavobacterium species.
U.S. Pat. No. 4,859,594 discloses microorganisms separated from natural environments and purified and genetically modified, and a process for immobilizing these microorganisms by affixing them to substrates. The biocatalytic compositions are useful for the detoxification of toxin-polluted streams containing a wide class of toxicants.
Although the prior art discloses that certain microorganisms are effective for the degradation of N-phosphonomethylglycine, and that N-phosphonomethylglycine can be biodegraded in an industrial pond, such biodegradation requires a significant amount of time to achieve substantial degradation of the N-phosphonomethylglycine. Now there is provided a mixture of microorganisms that have been conditioned to degrade N-phosphonomethylglycine and their use to degrade N-phosphonomethylglycine in a very short period of time and with a high degree of effectiveness.